Solid film lubricant and method for lubricating cycling low-high temperature friction surfaces

ABSTRACT

A method for lubricating surfaces subject to cycles of high-low temperature conditions by electro-deposition of a solid film lubricant having strong chemical bonds with the substrate surface, the lubricant containing gold and a refractory metal and oxides thereof, the film lubricant being deposited from an aqueous solution of a potassium gold cyanide consisting essentially of 5 to 15 grams per liter potassium gold cyanide, a highly ionizable refractory metal compound the metal constituent of which is selected from the group consisting of molybdenum, rhenium, ruthenium and tungsten, the quantity of metal compound at or exceeding 5 grams per liter, and the solution containing a nonreducible conducting salt of up to about 150 grams per liter, deposition being at a solution temperature of 140*F to to 160*F and a controlled solution voltage of 1.4 to 2.0 volts versus a saturated calomel electrode, the solution and deposition being controlled so that the solid lubricating film deposited has a concentration of about 2% to 50% by weight of the refractory metal oxides, the remainder being essentially gold and said refractory metal.

United States Patent l l Krienke et al.

[ Oct. 7, 1975 I SOLID FILM LL'BRICANT AND METHOD FOR LUBRICATING CYCLING LOW-HIGH TEMPERATURE FRICTION SURFACES [73] Assignee: General Dynamics Corporation, Fort Worth. Tex.

22 Filed: Jan. 24. 1973 21 Appl.No.-.326,406

[52] U.S. Cl. .i 29/1835; 29/196; 29/l99; 204/32; 204/43 G; 204/46 G [51] Int. Cl..... B23? 3/00; C25D 3/48; C25D 3/62 [58] Field of Search 204/46. 43 (1.56.32; 129N835 199. I96

[56] References Cited UNITED STATES PATENTS 2,754.258 7/l956 Taormina et al. 204/43 (3 3,475,292 10/1969 Shoushanian 3.530.049 9/l970 Scherzer et al i. 204/43 G FOREIGN PATENTS OR APPLICATIONS 928.083 6/1963 United Kingdom i. 204/43 G Primary Examiner-G L. Kaplan Attorney, Agent, or FirmCharles E. Schurman; Charles C M. Woodward ABSTRACT A method for lubricating surfaces subject to cycles ot higlrlow temperature conditions by electro deposition of a solid film lubricant having strong chemical bonds with the substrate surface, the lubricant containing gold and a refractory metal and oxides thereof the film lubricant being deposited from an aqueous solution of a potassium gold cyanide consisting essentially of 5 to [5 grams per liter potassium gold cyanide, a highly ionizable refractory metal compound the metal constituent of which is selected from the group consisting of molybdenum, rhenium, ruthenium and tungsten, the quantity of metal compound at or exceeding 5 grams per liter, and the solution containing a nonreducible conducting salt of up to about lSO grams per liter. deposition being at a solution temperature of l40F to to 160F and a controlled solution voltage of l.4 to 2.0 volts versus a saturated calomel electrode the solution and deposition being controlled so that the solid lubricating film deposited has a concentration of about 2% to 50% by weight of the refractory metal oxides, the remainder being essentially gold and said refractory metal.

10 Claims, 4 Drawing Figures US. Patent 0a. 7,1975 3,910,774

ROBERT D. KRIENKE JOHNNY W. HEAD HAROLD C- HOFFMAN EARL W. TURNS I N VE NTORS Fig. 4 lav/WWW ATTORNEY SOLID FILM LUBRICANT AND METHOD FOR LUBRICATING CYCLING LOVV-HIGH TEMPERATURE FRICTION SURFACES The present invention is a continuation-in-part of our copending application Ser. No. 63.637. filed Aug. 13. 1970 and now abandoned. which was a continuationin-part of application Ser. No. 812.947 filed Mar. 3, 1969 now abandoned, which was a continuation-inpart of application Ser. No. 537,256, filed Mar. I6. 1966 now abandoned. each relating generally to thin film solid constituent lubricants.

BACKGROUND OF THE INVENTION Numerous present lubricants in general are inadequate because basic requirements of some lubrication systems have escalated with the advent of more demanding bearing applications. These complex bearing applications require increased reliability and extended operational life at extreme temperatures and loads ne cessitating the search for longer life lubricants which maintain high lubricity under demanding environmental and load conditions. The available state-of-the-art solid film lubricants are operable only within a relatively narrow band of temperatures, and at relatively high coefficients of friction. thus exhibiting abbreviated wear lives.

The prior art reveals no method or process for providing the structure of the present invention either for the use intended. i.e.. a solid film lubricant. or for any other purpose. Generally, electroplating of metallic elements is accomplished by deposition from as pure an electrolytic bath as possible to reduce porosity and prevent stress cracking. In addition, the rate of plating is usually fast. for with the commonly used noble metals rapid plating engenders the desired dense, corrosion resistant. bright, esthetically pleasing depositv This is more fully explained in Metal Finishing Guidebook for 1965. Gold Plating, page 239. wherein the author cautions against permitting occlusions in the electrolytic bath. i.e., plating from a high impurity bath, and use of improper speed and current density which can result in formulation of undesired alloys and poor porosity. Further. the author therein states that if caution is not exercised, this poor porosity will permit the substrate or basis metal to oxidize and form an undesirable oxide layer on the surface of the plated material. Generally. electroplating as practiced in present state-ofthe-art is employed for depositing corrosion resistant coatings. high current conductors and for beautifying common metals. Obviously, porosity and oxidation would not be desirable for these applications.

There are many references to the detrimental effects of porosity and oxide contamination in the current lubrication literature and suggested methods following known art processes to increase the efficiency of the electroplating bath. The present invention is electroplated in direct conflict to the teachings of the art to form the herinafter disclosed novel structure which is distinguished from the bright. dense. relatively hard corrosion resistant platings referred to above.

The science of solid film lubrication is an infant field and much study and many theories have been presented on the mechanism through which solids lubri cate. The two generally accepted authorities. F. P. Bowden and D. Tabor. have postulated the most gener ally accepted theory. hereinafter discussed in order to establish a more complete understanding of the lubrication mechanism of the present invention.

This theory states. in part. that the actual area of contact between two unlubricated components, i.e., the basis or substrate materials, is generally much smaller than the apparent area. This is due to surface roughness or irregularities, which are in the form of integral protuberances or asperities inherent upon these surfaces. Therefore, it follows that, as adjacent materials are forced together in loading. the quasi-conical protuberances or asperities which contact opposite surfaces deform plastically until the area of contact is sufficient to support the imposed load. As the components are moved in relation to each other, the asperities are forced up and over one another, provided the asperities have slopes which are not too abrupt, in which case, they are smeared or deformed.

If, however, the meeting edges of the irregularities are too abrupt and thus not readily deformed, they form minute friction welds upon collision which are subsequently broken as sliding continues. Obviously, the presence of a lubricant. whether it be solid or liquid, upon these surfaces fills the valleys between asperities, thus reducing the area of the irregularities which can contact, and providing an intermediate which precludes friction welding. Even when lubricated. there is experienced during the first few cycles of movement or run in period" the greatest friction, which is subsequently reduced with each cycle due to substrate deformation and smearing, which reduces the severity and abruptness of the contacting asperities, hence lowering the coefficient of friction. During this run in period" the coefficients of friction are relatively high, as stated above. thereby requiring very high starting torques. As the interposed lubricant is destroyed or lost due to thermal decomposition or other factors affecting such materials, the raw basis metals are again permitted to rub together resulting in debris which is inherently abrasive in character, causing the surface to be more rapidly abraded away and resulting in ever greater surface roughness and erosion. materially advancing complete failure. This significantly decreases wear life and eventually will permit complete friction welds between substrates.

ln conditions where environments and loads are encountered which would be intolerable to fluid lubricants, a solid film" lubricant may be utilized to effect lubricity when applied to at least one of the adjacent surfaces. Several typical, multiconstituent solid film lubricants of the present art are molybdenum disulfide, boron nitride, and graphite.

These solid film lubricants all function similarly since they have in common a lower shear strength than the basis metal or substrate which they are intended to lubricate. This low shear strength is due to intrinsically weak Van der Waals bonds within the lubricant between adjacent crystalline layers, which are generally arranged in a striated manner. Such lubricants, however. must possess chemically strong bonds between adjacent crystals of a single layer to provide a good compressive strength and preclude penetration by the surface asperities. Gross penetration of such asperities would detrimentally affect the lubricant effectiveness. Obviously. a portion of some of the asperities will contact due to pressure and movement. however. the solid lubricant between adjacent surfaces will prevent formation of a friction weld, thus reducing associated friction and debris.

In such lubricants the lamellar structure will shear along internal intrinsic slip planes between layers of crystals upon movement of the components relative to one another. Further, it is felt that a minute localized melt may occur along such slip planes, further augmenting slippage while simultaneously holding the substrates apart. In this manner. friction is markedly reduced and wear life increased over that occurring during substrate metal to substrate metal contact.

Such a system functions well in many applications where fluid lubricants are not practical due to their inherent limitations. Solid films function relatively well except for one very deleterious characteristic found in both fluid lubricants and present solid film lubricants. As asperities of adjacent materials contact, collide and deform, they wipe or push the lubricant off the loaded area of contact and subsequently deposit it as debris in the valleys between asperities. As the substrates pass back over the thus unprotected area, friction is created even though a portion of the debris may" be redeposited. However, with each removal and redeposition, the lubricant is progressively lost due to thermal decomposition and physical displacement until lubricity is destroyed.

As the environmental factor becomes worse, as by the influence of external elevated temperature inputs, the structural integrity, such as compressive strength of the lubricant coating, is seriously affected. Furthermore, thermal decomposition and sublimation is significantly increased, resulting in an associated loss of lubricating material and capability.

The nearest appearing approach to the operational characteristics of the present invention there is no revealed approach to the structure, mechanism or process thereof resides in a state-ofthe-art solid film lubricant comprised of a composition of gold, molybdenum, and graphite which is contained in, and bonded to the substrate by a matrix of sodium silicate. This lubricant still exhibits the deleterious characteristics above noted. The sodium silicate matrix binder adheres mechanically, which adhesion is not reliable since it is inherently weak and is easily decomposed at high temperature. A reliable lubricant-substrate bond is essential, since strength must be sufficient to encourage internal shearing rather than shearing of the lubricant substrate bond which destroys the thin film of lubricant. This lubricant is reported to be operative from about -80 to 1,200F. At a room temperature environment it has a coefficient of friction of about 0.05; to 0.08;; and a wear life of approximately 90,000 cycles in a Hohman A-6 tester, or 66,600 sliding feet. As temperature increases, however, the coefficient of friction rapidly approaches 0.1 at I200F., and wear life is reduced to only 1200 cycles or 888 sliding feet. Normally, only one low-high temperature utilization is possible with this lubricant, and it is thus obviously unsuitable for any cycling application so critical in aerospace technology.

SUMMARY OF THE INVENTION The present invention, by contrast to the prior art discussed above, provides for the first time a lubricant and method for lubricating which is not only superior to all known lubricants for high temperature application. but is capable as well of repeated cycling from below F., through room temperature to high temperatures, and back repeatedly.

More specifically, the invention concerns an electrocodeposited thin solid film lubricant comprised of a unique combination of constituents forming a novel, randomly discontinuous, ductile physical structure possessing a plurality of related, overlapping lubricating mechanisms which combine to provide exceptional lubricity throughout extended environmental conditions, and which is capable of regenerating such lubricating mechanisms from within its own structure during operation, thus greatly extending the effectiveness and life of the inventive lubricant.

The lubricant of the present invention is electrodeposited as a soft mallable matrix on the substrate to form a film which establishes chemical bonds between the deposited lubricant and the substrate. These chemical bonds are intrinsically strong and are a prime factor in providing a good reliable lubricating system. Further, electrodeposition in combination with the proper constituents results in the deposition of the inventive porous structure and the proper included constituents to achieve the excellent lubricity of the invention.

The essential constituents of the film matrix include a soft, malleable gold matrix material in combination with a second constituent of a refractory or super alloy metal and oxides thereof selected from the group consisting of molybdenum, rhenium, ruthenium and tungsten. This lubricant must be plated upon the proper substrate, as will be hereafter discussed, in that its oxides perform an important function in good high temperature lubrication. It is postulated that the new solid film lubricant of the present invention employs three separate and distinct mechanisms to effect lubricity. The first of these mechanisms is seen to reside in the formation of a solid film lubricant having a concentration of the refractory metal salt or oxides thereof of about 2% to about 50% by weight which raises the melting temperature of the matrix and has intrinsic slip planes conducive to intercrystalline shear. This mecha nism operates, it appears in combination with encapsulated metal inclusive particles, which on exposure to air take the form of lubricating oxides, forming the second mechanism. These oxides further weaken intercrystalline bonds and are subsequently deposited upon the substrate surface as required by environmental factors through oxide diffusion.

The remaining mechanism functions in combination with the replenished surface oxides stored in the matrix, as a dispersion of metal particles, and functions in much the same manner. However, these oxides are derived from the metal inclusive particles stored in the substrate and are generally more effective during high temperature operation. All of these mechanisms combine to provide the wide range of lubrication offered by the present invention.

Therefore, it is the salient objective of the present invention to provide a solid film lubricant comprising associated included constituents providing a novel porous discontinuous structure, in combination with the proper lubricant-substrate relationship, which is capable of superior lubrication in extreme environments unobtainable in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS In the figures:

FIG. 1 is a photomicrograph at 100 magnification of unetchcd gold electrodeposited upon a T-l tool steel substrate in a conventional gold plating manner and illustrative of prior art.

FIG. 2 is a photomicrograph at I00 magnification of the structure of the present invention. wherein the specimen is unetched and the constituents comprise a gold matrix codeposited with a molybdenum alloying metal and oxide on a tungsten alloy tool steel substrate.

FIG. 3 is a photomicrograph of the surface of a gold molybdenum lubricant of the present invention at 400 magnification, showing solid solution of the gold and molybdenum constituents, their porosity and the resulting capillaries.

FIG. 4 is an electron microscope photograph at [3,500 magnification of several gold molybdenum crystals revealing again the solid solution state and the included molybdenum particles.

Reference is now made to FIG. 1, wherein a conventional gold plate is illustrated. It is quite obvious from inspection thereof that a dense continuous structure is presented effecting a continuous coating over the substrate 12. This type of structure is typical of the kind achieved in state-of-the-art plating, and requires a highly pure, inherently lowpore, low-occlusion electrolytic bath. A bath of this type is necessary to insure deposition of a pure gold film, such as is seen at 10, in FIG. 1. This bath or solution prevents the formation of a gold-substrate metal alloy which the prior art teaches is undesirable. It is also stressed in state-of-the-art literature that every precaution should be taken to prevent intermixing of the metals which deleteriously effects the permeability of the coatings. The prior art teaches that the deposited coating must be continuous, as at 14, to prevent substrate oxidation. which would cause oxides to form upon the outer surface 16 of the coating. The lack of oxidation at the gold-substrate interface 18 is readily apparent in FIG. I, and the effectiveness of the conventional plating method to achieve a substantially homogeneous, uniform gold deposit is apparent.

One system of the present invention is shown in FIG. 2, which is a I00 magnification photomicrograph of an electrocodeposited gold-molybdenum film 20 and tungsten alloy tool steel substrate 22. As is apparent, this system comprises a solid film 24 of gold and encapsulated molybdenum, and molybdenum oxide particles (not visible in FIG. 2, but apparent in the 13,500 magnification of FIG. 4). Film 20 contains microscopic cracks 26 which, through intercommunication, extend to substrate 22 from surface 28. The dark oxide area 30 at the film-substrate interface is particularly obvious.

FIG. 3 is a photomicrograph at 400 magnification of the surface of the FIG. 2 system. Inspection of FIG. 3 reveals the cracks 26 appearing in surface 28 of the gold-matrix molybdenum film, and is illustrative of the extension of cracks 26 to substrate 22, the bright portion indicated by reference numeral 32 being a reflection from the substrate. The remaining molybdic acid salts are electroreduced to molybdenum oxide particles, and these are in turn encapsulated by subsequent deposition of the solid film gold-matrix. Consequently, these particles share few chemical bonds with surrounding atoms and thus materially enhance subsequent oxide diffusion or migration.

The novel porous. discontinuous structure, as illustrated in FIGS. 2 and 3, are created and deposited through control of various critical conditions main tained during plating, as subsequently explained in detail. In general, the concentration is important as one control, since the higher the concentration of metal ions the more dense the deposit will be. Conversely, when the concentration is too low for reduction. the potential of the cathode rises and hydrogen ions are deposited. The hydrogen occupies a portion on the substrate or prior-deposited layer, momentarily excluding the metal ions. When the hydrogen subsequently evolves or escapes a void is left which is not readily filled because it constitutes a low spot and electrically deposited ions are attracted to the higher portions.

Temperature of the electrolytic solution is important, as hereinafter explained, in that a low temperature has the same effect as a low concentration upon porosity. An additional important factor is current density here after expressed in its more meaningful term, control voltage. With voltages above that herein specified, hydrogen evolution is so great that the deposit is loose and granular or noncoherent, conversely a control volt age below the parameters given results in a nonporous deposit since no hydrogen evolution occurs. Another significant factor is the impurity of the solution or the presence of occlusions. As the secondary constituents are primarily deposited as metal and oxides, they are impurities which decrease current efficiency in the plating procedure and hence increase hydrogen evolution, thus generating porosity. Presently accepted techniques are predicated on the fact that non-metallic occlusions in molybdenum plating result in unsound plating clue to visible detrimental cracking.

Such porosity or inherent cracking of the film structure appears important to the present invention since the pores, voids or cracks evidently function as capillaries and permit air to oxidize the substrate material, as may be noted at 30 in FIG. 2 at the lubricant-film substrate interfaces. It is thus surmised also that such oxides formed are caused by thermal diffusion, resultant from elevated surface temperature generated by friction during operation, to migrate to an area upon or near the surface of the film.

Differential thermal analysis and thermal gravimetric analysis reveal that in the gold-molybdenum system, for example, the oxides resulting from the molybdenum particles encapsulated within the film are, at elevated temperature, molybdenum trioxide. It is of course known that M00 is an excellent high temperature lubricant and that molybdenum oxide functions well at low temperatures. The present invention is seen, then, to make it possible to store or retain large quantities of metals readily converted to oxides within its structure or system and subsequently release them on an as required basis through migration to the surface, the type of oxide released being dependent on the temperature and most suitable thereto. Such inclusions are readily apparent in FIG. 4.

Referring now to FIG. 4, which is a 13,500 magnification of the gold-molybdenum system of FIGS. 2 and 3, the film crystals are clearly seen to contain inclusions 72.

The present invention is operative to permit lubrication from about F. to above 1,500F. At -80F. the coefficient of friction, as recorded repeatedly on a Hohman A-6 tester, is approximately 0.1 and ranges to a low of 0.02" at 1,l50F. At room temperatures, the dynamic coefficient of friction is about 0.04 and static about 0.055. In all tests of the films of the present invention at l,l50F., and up to l,500F., the wear life exceeded one million cycles or 720,000 sliding feet. an increase of a thousand fold over known solid film lubricants. At that point the tests were terminated even inherently weak bonds between an oxide and the main lubricant structure.

The structure of the lubricant of the invention evinces good compressive strength due to the solid film though the coefficient of friction of the lubricant had lubricant which permits only occasional contact of adnot exceeded or reached 0.4. an arbitrarily selected but jacent asperities. However, periodically the adjacent generally accepted value as regards adequate lubricity. asperities will contact under high load, thus wiping the The load carrying capability of the lubricant has been surface oxides and lubricant structure away from the amply demonstrated by use on movable wing superarea of load, and unlike existing lubricants, the oxides sonic aircraft. It) thus removed are immediately replaced by *stored FlG. 2 amply illustrates the required structure which f h slh'muhihg l' thus Providing plays an important role in [he lubricam's Operation AS lUlZJflCaIlOfl'Unlll the matrix structure IS shoved back by, above stated, the mechanisms of lubrication according P" redeposhcd durmg- Subsequent Passes of the WW to the present invention are the formation of a solid lumg Surfacebricating film which engenders strength and internal AS the operahfmal tcmimr'fmllre other P slip planes, suitable lubricating oxides which are stored "Omaha ehhahcmg the efflclehcy of the lhvehhoh within the structure as metallic inclusions, and porosity elhvalcd p r ure he molecules of the or cracks, to permit oxidation of the substrate and pro- 'h at rapld rate, augmenting y vide capillaries for migration of the substrate oxides or talhhe Shem? Whlle the p f y h becomes the converted stored oxides to the surface as required Oxides! w molybdenum h'loxlde which greatly h by environment hances lubrication. The elevated temperature and air causes the exposed substrate to oxidize at a more rapid i p ihese mechamsnis comnblnes to lubncatlve rate and subsequently creates thermal diffusion resultabihty in different ways which combined lend superior ing in migration of substrate Oxides to the surface, lubricity over an extended range of environments. The hence flooding the running surface with the needed structure enjoys a reliable, inherently sound chem|cal ides bond with the Substrate material Tests conducted with various deposition techniques During low temperature operation, internal shear ocand solutions, and of a gold-molybdenum system accurs as the intercrystalline bonds are weakened by the cording to the invention are tabulated in Table l below:

TABLE I Lubricity Surface Deposit Condition Composition Deposition Con ditions Current Density-Potential Temp. Rate 1 Conventional Poor Silver DenseSemibright I20F -100 amps/sq.ft. Relatively Fast 2 Silver From AgRe Bath) Porous-Dull Good [.4 volts** CD. 2 amps/sqft.

.0005" 30 Min.

3 Ag-Re Porous-Dark Good Varies with Reconcentration in Deposit E L4 volts C.D. 2 ampslsqft.

.0005" 30 Min.

4 Conventional Poor Gold Bright-Dense KAu(CN] ISg/l Sod. Citrate SOg/l PH 7.6

5 Au-Mo Dark-Somewhat Good Porous l5UF E 1.7 volts .0004" 5 Min.

5 Min.

Sod. Citrate SOg/l H,MoO..H,O 25g/l PH 7.6

g/l Grams Per Liter "vs Saturated Calornel Electrode The results of the above tests appear to prove conclusively that the porous discontinuous structure taught by the present invention is a prime consideration in achieving superior lubrication.

The gold-molybdenum lubricant of the above example was deposited from an aqueous solution which contained a potassium gold cyanide bath comprising 15 grams per liter potassium gold cyanide, 25 grams per liter molybdie acid and 50 grams per liter sodium citrate. Sodium citrate was utilized as a non-reducible conducting salt in this solution. The constituents were plated at 1.7 volts plus or minus 0.1 volt versus a saturated calomel electrode. The temperature of the solution was from 150 to 160F. employing a suitable agitation mechanism. Platinum anodes are employed for best results.

Examples of other lubricating gold-alloy solutions in accordance with the present inventiion are given be low. the constituents of the potassium gold cyanide bath being in grams per liter unless otherwise designated and giving both the operative general range and a specific formulation. Temperature given is that of the plating solution in degrees Fahrenheit. and the control voltage (CV) is expressed in volts versus a saturated calomel electrode. In each instance. to achieve satisfactory lubricity, the solid film deposited must have a concentration of the refractory metal oxides or oxides of 2% to 50% by weight the preferred range being 2.4 to 40.1%. and a thickness of 0.0002 to 0.001 inches, the preferred range being 0.0004 to 0.0015. The pH is unimportant as long as the composition of the solution is within the range specified. since plating in accordance with the present invention is not controlled by pH nor does it generally require pH control, although such control may be utilized as a matter of convenience. The first example given is, in each instance, the preferred solution. General ranges are given in subsequent examples only where the solution ingredient is not shown in the first or prior examples.

(iold Molybdenum General Specific 1. Potassium (jold Cyanide KAulCN], 5-15 15 Sodium Citrate Na C H -,O-,.2H,O 50-100 50 Molybdic Acid H MoO..H 5-50 25 Temperature. F 140-160 150 C. V. v. SCE 1.4-2.0 1.7 pH 5.0-1 1.0 7.6 2. KAuICN): 15 Sodium Citrate I Molyhdie Acid 25 Sodium Molybdate NU IMOOyZH- O -h0 25 Temperature, F 140 C. V. v. SCE 2.0 pH 7.6 3 KAul (N 7.5

Sodium Citrate 50 Molyhdic Acid .50 Temperature. l- 150 C. V. SCE 1.7 pH 7.1 4. KAulCNh 7.5 Sodium Citrate 50 Sodium Molybdate 60 Temperature. F 150 C. V. v. SCE 1.7 pH 10.2 5. KAu(CN]. 7.5

Sodium Citrate I00 Molyhdic Acid 25 Sodium Molyhdate 25 Temperature, F 150 C. V. v. SCE 1.4 pH 3.3 6. KAu(CN);. Sodium Citrate 100 Molybdic Acid 25 Citric Acid 25 Temperature. "F 140 C. V v SCE 2.0 pH 5.2 7 KAutCN): 5 Sodium Citrate I00 Molybdie Acid 7.5 Temperature. "F l. 0 C. V. \v SCE 1.7 pH 7.1

Gold Rhenium General Specific Iv KAutCNl 5-15 15 Sodium Citrate 0-150 Sodium Perrhcnate NaReO 5-15 15 Citric Acid H;,C,.H O.-.2H O 0-25 25 Temperature, F -160 140 C. V. v. SCE 1.2-1.75 1.7 pH 5.20 2. KAutCN), 5 NaReO 5 Disodium Phosphate Na HPO .l2H O 5 Temperature. "F 140 C. V. v. SCE 1.4 pH 5.2 3. KAutCNh 5 NaReO. 10 Disodium Phosphate 5 Temperature, F 140 C. V. v. SCE 1.4 pH 52 Gold Tungsten General Specific 1., KAutCN) 5-15 15 Rochelle Salt KNaC H O 4-H O 0-100 100 Ammonium Chloride NH,C[. 0-25 25 Ammonium Hydroxide NH OH 0-50ml 50ml Sodium Tungstate Na- WO .2H,O 5-15 15 Temperature. "F 140-160 C. V. v. SCE 1.4-2.0 1.7 pH 5.0 5.2 2. KAu(( N) S Disodium Phosphate Na HPo llH O 0-5 5 *Potassium Cyanide KCN 0-15 15 Sodium Tungstatc 5 Temperture. "F 140 C. V. v. SCE 1.4 pH 5.2 3. KAu(CN)., 5 Disodium Phosphate 5 "*KCN I5 Rochelle Salt I00 Ammonium Hydroxide 37ml Sodium Tungstatc 5 Temperature, F 140 C. V. v. SCE 1.75 pH 5.2 4. KAu(CN) 15 Sodium Citrate 0-150 150 Citric Acid 0-25 25 Sodium Tungstate 7.5 Temperature. F 140 C. V. v. SCE 1.7 pH 5.2

Gold Ruthenium General Specific l. KAu(CN), 5-15 Disodium Phosphate 0-5 5 *Potassium Cyanide 0-15 15 Ruthenium Sulfamate 5-15 5 Ru(OSO.,-NH Temperature. "F 140-]60 140 C. V. v. SCE 1.4-2.0 pH 10.0 10.2

Ammonium chloride a pears to act as a eomplexing agent and aids in holding the pH stable. "Ammonium hydroxide may be used for pH modification. '"Potassium cyanide may he used for the free cyanide and to enhance the conductivity without eleetro-rcducing.

From the above, the generally exemplary electrolytic solutions of the present invention may be summarized in the following Table I1:

TABLE [1 Refrac- Con- Solid tory duct- Film KAu Metal irlg Control Temp. Lubri- (CN Compound Salt Voltage F cant 5-15 g/l 5-60 g/l 5-150 g/l 1.4-2.0 140-160 vs SCE Gen. 5-15 5-60 5-125 AuMo Pref. 25 50 AuMo Gen. 5-15 5-15 5-125 AuRe Pref. I5 15 125 AuRe Gen. 5-15 5-15 5-15(] AuW Pref. l5 15 150 AuW Gen. 5-15 5-15 AuRu Pref. 5 5 AuRu The plating is done upon a suitable cleaned substrate. Cleaning is generally accomplished by wiping the substrate with methyl ethyl ketone, subsequently degreasing with triehloroethylene, and grit blasting with 120 mesh aluminum oxide (A1 03). after which the substrate is alkaline electrocleaned in a nonsilicated alkaline cleaner. 1f the film of the invention is to be deposited upon chrome steels or high carbon steels a preliminary nickel strike may be required. This strike consists of immersing in aqueous solution containing 16 ozs. per gallon nickelous chloride (NiCl and 8 02s. per gallon hydrochloric acid (HCl) at room temperatures. Nickel anodes are employed. The substrate receives an anodic treatment at 5 amps per square foot for 30 seconds and 2. The method defined by claim 1 wherein said molybdenum compound is H MQOFH O in an amount of about 25 grams per liter, said non-reducible conducting salt is sodium citrate in an amount of about 50 grams per liter, said solution temperature being maintained at or about 150F and said control voltage being maintained at or about 1.7 volts.

3. An aqueous plating bath solution for electrodeposition of a porous, malleable, soft but coherent solid film lubricant of a gold, refractory metal and at least one oxide of the refractory metal as a matrix or alloy thereof on a substrate and consisting essentially of:

a. from 5 to 15 grams per liter potassium gold cyanide,

subsequently a cathode treatment at 7.5 amps per b. an ionizable molybdenum compoundin an amount square foot for 90 seconds, and an immediate rinse in belwee" 5 and 60 grams P f P tap wast substantial plateout of molybdenum m oxide form The present invention is thus seen to reside in a and metal Convemble F oxlde m 1 lubncanh novel, discontinuous porous structure and process for at least one nnn'reduclble Fonductmg salt g deposition thereof which possesses intrinsic intermo- 5 to grams l of bath solunon or lecular shear planes and oxide convertible inclusions l Fonducmfltyt which function in combination as both a low and high S0luun bemg effecuve to depos" on the temperature lubricant in a highly superior manner unastrata the 'i porous Soft malleable coherent chievable b statefihhedn means SOllCl film lubricant under a solution control of y 40 about 1.4 volts to 2.0 volts versus a saturated calo- We claim:

1. A method for lubricating surfaces movable relative to one another by providing on at least one such surface a porous, malleable, soft but coherent solid lubricant of metal and metal oxide comprising:

A. cleaning at least one of said surfaces,

B. depositing thereon a solid film lubricant essentially comprised of a matrix of gold with a refractory metal and at least one oxide thereof from an aqueous solution of potassium gold cyanide consisting in essence of:

1. from 5 to 15 grams per liter potassium gold cya nide,

2. an ionizable molybdenum compound in an amount between 5 and 60 grams per liter for providing a substantial plateout of molybdenum in oxide form in said lubricant,

3. at least one non-reducible conducting salt of from about 5 to 150 grams per liter of solution,

C. maintaining the temperature of the solution at from 140 to 160F, and,

D. closely controlling the plating solution voltage versus a saturated calomel electrode at from about 1.4 volts to 2.0 volts,

the solution and deposition being controlled to deposit a solid film lubricant having a concentration of molybdenum oxide therein in an amount of about 2% to 50% by weight of said deposited film, the remainder being essentially gold.

mel electrode.

4. The aqueous plating bath of claim 3 in which said ionizable compound is a molybdic salt of from about 5 to about 60 grams per liter so that the solid film lubricant deposited has a concentration of said refractory metal oxide of from 2.4 to 40.1% by weight.

5. The aqueous plating bath of claim 3, in which said ionizable compound is a molybdic acid of from 5 to about 60 grams per liter so that the solid film deposited has a concentration of said refractory metal oxide of from 2.4 to 40.1% by weight.

6. The aqueous plating bath solution of claim 3, wherein said potassium gold cyanide is present at about 15 grams per liter, said compound is H2MoO H O present at about 25 grams per liter, and said nonreducible conducting salt is sodium citrate at about 50 grams per liter.

7. An article made in accordance with claim 1.

8. The article of claim 7 in which the solid lubricant has a deposited thickness in the range from about 0.0002 to about 0.00] inches.

9. The article of claim 7 in which the solid lubricant thickness is in the range from about 0.0004 to about 0.0015 inches.

10. The article of claim 7 in which said oxide concentration in the lubricant is in the range of 2.4 to 40.1% by weight. 

1. A METHOD FOR LUBRICATING SURFACES MOVABLE RELATIVE TO ONE ANOTHER BY PROVIDING ON AT LEAST ONE SUCH SURFACE A POROUS, MALLEABLE SOFT BUT COHERENT SOLID LUBRICANT OF METAL AND METAL OXIDE COMPRISING: A. CLEANING AT LEAST ONE OF SAID SURFACES, B. DEPOSITING THEREON A SOLID FILM LUBRICANT ESSENTIALLY COMPRISED OF A MATRIX OF GOLD WITH A REFACTORY METAL AND AT LEAST ONE OXIDE THEREON FROM AN AQUEOUS SOLUTION OF POTASSIUM GOLD CYANIDE CONSISTING IN ESSENCE OF:
 1. FROM 5 TO 15 GRAMS PER LITER POTASSIUM GOLD CYANIDE,
 2. AN IONIZED MOLYBDENUM COMPOUND IN AN AMOUNT BETWEEN 5 TO 60 GRAMS PER LITER FOR PROVIDING A SUBSTANTIAL PLATEOUT OF MOLYBDENUM IN OXIDE FORM IN SAID LUBRICANT,
 2. The method defined by claim 1 wherein said molybdenum compound is H2Mo04 - H20 in an amount of about 25 grams per liter, said non-reducible conducting salt is sodium citrate in an amount of about 50 grams per liter, said solution temperature being maintained at or about 150*F, and said control voltage being maintained at or about 1.7 volts.
 2. an ionizable molybdenum compound in an amount between 5 and 60 grams per liter for providing a substantial plateout of molybdenum in oxide form in said lubricant,
 3. at least one non-reducible conducting salt of from about 5 to 150 grams per liter of solution, C. maintaining the temperature of the solution at from 140* to 160*F, and, D. closely controlling the plating solution voltage versus a saturated calomel electrode at from about 1.4 volts to 2.0 volts, the solution and deposition being controlled to deposit a solid film lubricant having a concentration of molybdenum oxide therein in an amount of about 2% to 50% by weight of said deposited film, the remainder being essentially gold.
 3. An aqueous plating bath solution for electrodeposition of a porous, malleable, soft but coherent solid film lubricant of a gold, refractory metal and at least one oxide of the refractory metal as a matrix or alloy thereof on a substrate and consisting essentially of: a. from 5 to 15 grams per liter potassium gold cyanide, b. an ionizable molybdenum compound in an amount between 5 and 60 grams per liter for providing a substantial plateout of molybdenum in oxide form and metal convertible to oxide in the lubricant, c. at least one non-reducible conducting salt of from about 5 to 150 grams per liter of bath solution for providsolution conductivity, d. said solution being effective to deposit on the substrate the desired porous, soft, malleable, coherent solid film lubricant under a solution control of about 1.4 volts to 2.0 volts versus a saturated calomel electrode.
 3. AT LEAST ONE NON-REDUCIBLE CONDUCTING SALT OF FROM ABOUT 5 TO 150 GRAMS PER ALITER OF SOLUTION, C. MAINTAINING THE TEMPERATURE OF THE SOLUTION AT DROM 140* TO 160*F, AND, D. CLOSELY CONTROLLING THE PLATING SOLUTION VOLTAGE VERSUS A SATURATED CALOMEL ELECTRODE AT FROM ABOUT 1.4 VOLTS TO 2.0 VOLTS, THE SOLUTION AND DEPOSITION BEING CONTROLLED TO DEPOSIT A SOLID FILM LUBRICANT HAVING A CONCENTRATION OF MOLYBDENUM OXIDE THEREIN IN AN AMOUN OF ABOUT 2% TO 50% BY WEIGHT OF SAID DEPOSIT FILM, THE REMAINDER BEING ESSENTIALLY GOLD,
 4. The aqueous plating bath of claim 3 in which said ionizable compound is a molybdic salt of from about 5 to about 60 grams per liter so that the solid film lubricant deposited has a concentration of said refractory metal oxide of from 2.4 to 40.1% by weight.
 5. The aqueous platiNg bath of claim 3, in which said ionizable compound is a molybdic acid of from 5 to about 60 grams per liter so that the solid film deposited has a concentration of said refractory metal oxide of from 2.4 to 40.1% by weight.
 6. The aqueous plating bath solution of claim 3, wherein said potassium gold cyanide is present at about 15 grams per liter, said compound is H2Mo04. H20 present at about 25 grams per liter, and said non-reducible conducting salt is sodium citrate at about 50 grams per liter.
 7. AN ARTICLE MADE IN ACCORDANCE WITH CLAIM
 1. 8. THE ARTICLE OF CLAIM 7 IN WHICH THE SOLID LUBRICANT HAS A DEPOSITED THICKNESS IN THE RANGE FROM ABOUT 0.0002 TO ABOUT 0.001 INCHES.
 9. The article of claim 7 in which the solid lubricant thickness is in the range from about 0.0004 to about 0.0015 inches.
 10. The article of claim 7 in which said oxide concentration in the lubricant is in the range of 2.4 to 40.1% by weight. 